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I don't know what your field function is , but DEFINE_DPM_SOURCE is acturally powerful.It's a way to get every particle messages in a cell and you can edit both this cell and particles in cell.Maybe you can make your flied function transform to it, or you program a field function udf,which can get the information.But I have never tried it.If you want to use DEFINE_DPM_SOURCE,you can read the ansys fluent's udf document.

Note:It's a huge work about learning.